Analysis of light quality and assemblage composition on diatom motility and accumulation rate

Abstract

2016): Analysis of light quality and assemblage composition on diatom motility and accumulation rate, Diatom Research,The photosensitive nature of pennate diatom movement has long been observed, with cells being able to change the direction of their movement depending on the light conditions detected at the tips of the cells. However, much of this evidence is based on observations of cells in isolated, single-species culture, thus devoid of any information regarding inter-species interactions that might occur in more complex assemblages. In this study, we tested light-sensitive diatom motility responses (cell accumulation into light spots and high irradiation-induced direction change) in the absence and presence of other species. In the light spot accumulation assay, each species showed characteristic accumulation rates with regard to light irradiance, wavelength, and presence of other species. In mixed-species assemblages, the relative abundance of different species present in the light spot could be directly modified by changes in ambient light conditions. Diatom cells were also irradiated at their leading or trailing ends in the presence or absence of other diatom species to determine the effect of assemblage composition on high irradiance photo-responsiveness. While most multi-species combinations resulted in no significant change in the high irradiance response, Stauroneis phoenicenteron cells showed a significantly slower blue light stimulated direction change response, dependent on relative cell abundance in the presence of Craticula cuspidata. Our experiments thus indicate that the rate of irradiation-stimulated direction change and accumulation ability are not only species-specific and dependent on light wavelength and intensity, but can also be modulated by the presence of other diatom species.

Light intensity and spectral composition drive reproductive success in the marine benthic diatom Seminavis robusta

“…The dependency of mating on blue light (and to a lower extent green light) in S. robusta and C. didymus 50 is in line with a general propensity of blue light to regulate various cellular processes in diatoms, such as cell cycle progression, phototaxis, vertical migration and production of metabolic compounds such as the pigment marennine 32 , 33 , 36 , 37 , 58 , 76 . The identification of functional red-light phytochromes in diatoms 19 and species-specific red light responses in motility and sinking 37 , 38 , 77 has recently challenged this perspective, suggesting that red light sensing plays a more important role in diatoms than was previously anticipated.…”

“…Cells generally move upwards towards the sediment surface under moderate light intensities and migrate deeper into the sediment in darkness and under very high light intensities, resulting in synchronized rhythmic migration patterns over diurnal cycles 32 – 35 . Illumination experiments covering different wavelength ranges have shown that phototaxis and surface accumulation of motile diatoms is in most cases dependent on the presence of blue light 32 , 33 , 36 , 37 . Stauroneis phoenicenteron , on the other hand, is attracted to low intensity red light, suggesting that different benthic species employ different types of photoreceptors 24 , 38 .…”

The Vertical Migratory Rhythm of Intertidal Microphytobenthos in Sediment Depends on the Light Photoperiod, Intensity, and Spectrum: Evidence for a Positive Effect of Blue Wavelengths

“…These interspecies differences in frustule optical properties were claimed to additionally modulate the light availability inside the biofilm itself (Goessling et al, 2018a). Taken together with the fact that a species response to BL can be modulated by the presence of other species in its close surrounding (Cohn et al, 2016), it points out to the importance of the species consortium composition, which varies year around (this study, Haubois et al, 2005). Therefore, wavelengths, together with irradiance, would fine tune the differential rhythmic MPB migratory behavior and surface PAB accumulation versus the sediment light climate at the cell, species, and consortium (i.e., biofilm) levels.…”

“…Although green light generated a similar PAB accumulation than BL for the same intensity (40 µmol photons m −2 s −1 ), our experimental setup did not allow to test higher green light intensities to unambiguously conclude the responses to green light. It was previously demonstrated that green light (>510-520 nm) generally has a lower effect than BL (450 ± 20 nm) on phototactic directional cell movements (Nultsch, 1971;Cohn et al, 2004Cohn et al, , 2015Cohn et al, , 2016. Differently, red light of low or moderate intensity usually has no/little effect or negative effect on directional motility of diatoms and their accumulation, although this response is species-specific (Cohn and Weitzell, 1996;McLachlan et al, 2009;Cohn et al, 2015).…”

“…A major growth form of MPB diatoms is epipelon, which mostly inhabits fine cohesive sediments and comprises raphid diatom species moving freely in between sediment particles. The motility of epipelic diatoms is ensured by a slit (raphe) in their cell wall (frustule), which allows for directional and reversible locomotion (Cohn, 2001;Cohn et al, 2016) driven by highly sophisticated suites of micromovements (Apoya-Horton et al, 2006;Bertrand, 2008). Motility is a key adaptation to the intertidal sedimentary habitat providing epipelic diatoms with many ecological benefits including the colonization of microhabitats with specific light, nutrient, and temperature conditions, coping with environmental extreme variations, optimization of photosynthetic productivity, pheromonalbased sexual attraction, and tidal resuspension avoidance (see Consalvey et al, 2004;Marques Da Silva et al, 2017;Nakov et al, 2018, and references therein).…”